Starch nanocomposite materials

ABSTRACT

In one aspect, the invention provides a substantially exfoliated nanocomposite material including starch and hydrophobically modified layered silicate clay. In another aspect, the invention provides packaging made from material including the substantially exfoliated nanocomposite material described above. The nanocomposite material has improved mechanical and rheological properties and reduced sensitivity to moisture in that the rates of moisture update and/or loss are reduced. In another aspect, the invention provides a process for preparing the substantially exfoliated nanocomposite material described above, including a step of mixing the starch in the form of an aqueous gel with the hydrophobic clay in a melt mixing device. In a further aspect, the invention provides a process for preparing the substantially exfoliated nanocomposite material, including the steps of mixing the starch with the hydrophobic clay to form a masterbatch (hereinafter “the masterbatch process”) and mixing the masterbatch with further starch.

This application is a National Stage Application of PCT/AU2008/000787,filed Jun. 2, 2008, which in turn claims priority to Australian PatentApplication No. 2007902980, filed Jun. 1, 2007.

FIELD OF THE INVENTION

The present invention relates generally to nanocomposite materials. Moreparticularly, the invention relates to nanocomposite materials whichinclude starch and a substantially exfoliated hydrophobic clay. Theinvention also relates to a process for preparing such nanocompositematerials.

In one particular aspect, the invention relates to a nanocompositematerial suitable for use in packaging materials and it will beconvenient hereinafter to describe the invention in relation to thatapplication. It should be appreciated, however, that the presentinvention is not limited to that application only, and may be applied toother applications.

BACKGROUND OF THE INVENTION

The following discussion is intended to facilitate an understanding ofthe present invention. However, it should be appreciated that thediscussion is not an acknowledgement or admission that any of the matterreferred to was published, known or part of the knowledge of the skilledworker at the priority date of the application.

Thermoplastic materials are typically prepared from hydrocarbon rawmaterials. Due to environmental problems associated with theirproduction and degradation, alternative materials have been developed.

One alternative is to use a natural polymer such as starch to makethermoplastic materials. Natural polymers originate from renewablesources and are intrinsically biodegradable.

Nanocomposites made from unmodified low amylose starch and unmodified orhydrophilic clays have been disclosed.

U.S. Pat. No. 6,811,599 discloses a biodegradable thermoplastic materialcomprising a natural polymer, a plasticiser and an exfoliated clayhaving a layered structure. The description refers to a need to choosean organic modificant of the clay for compatibility with the naturalpolymer. This suggests that a hydrophilic clay is desirable. A problemwith the material is that only partial exfoliation was obtained.

A paper by H Park et al, entitled “Preparation and properties ofbiodegradable thermoplastic starch/clay hybrids” in MacromolecularMaterials and Engineering 2002, 287, (8), 553-558, disclosesstarch-based nanocomposites based on both sodium montmorilloniteunmodified clay (CLOISITE™ Na⁺) and organic modified clays (CLOISITE™6A, 10A, and 30B). The most desirable mechanical properties wereobtained with the unmodified clay and little exfoliation or expansion ofthe clay structure was observed.

A paper by B Q Chen and J R G Evans, entitled “Thermoplastic starch-claynanocomposites and their characteristics” in Carbohydrate Polymers 2005,61, (4), 455-463, discloses nanocomposites based on glycerol-plasticisedthermoplastic starch. The clays used were sodium montmorillonite, sodiumhectorite, sodium hectorite modified with dimethyl di(hydrogenatedtallow) ammonium chloride and kaolinite. Samples were prepared by meltprocessing using a two-roll mill. Only the unmodified montmorilloniteand hectorite clays, both of which are hydrophilic, were reported togive partial exfoliation.

A paper by K Bagdi et al, entitled “Thermoplastic starch/layeredsilicate composites: structure, interaction, properties” in CompositeInterfaces 2006, 13, (1), 1-17, discloses the preparation of clay(nano)composites based on glycerol-plasticised wheat starch. The claysused were sodium montmorillonite and clay modified with aminiododecanoicacid (NANOFIL™ 784), stearyl dihydroxyethyl ammonium chloride (NANOFIL™804) or distearyldimethylammonium chloride (NANOFIL™ 948). No or onlylimited expansion of the clay was observed.

A paper by B Chiou et al, entitled “Rheology of starch-claynanocomposites” in Carbohydrate Polymers 2005, 59, (4), 467-475,discusses the rheology of thermoplastic starch-clay nanocomposites(clays used were CLOISITE™ Na⁺, CLOISITE™ 30B, 10A, and 15A). Variousstarches were examined, including wheat, potato, corn and waxy cornstarch.

International patent WO 2005068364 claims starch and modified starchesas intercalants for nanoclays. The method employed makes use of thewater-friendly nature of clay.

Nanocomposite materials based on starch and clay having a high degree ofexfoliation of the clay, and having improved properties including, forexample, a high degree of transparency, improved mechanical andrheological properties and/or reduced sensitivity to moisture, would bedesirable.

It has been found that use of a hydrophobic clay in the preparation of ananocomposite material results in surprising levels of improvement inthe properties of the resulting material, including in its clarity,pliability, tensile strength, impact resistance and/or tensileproperties.

Thus in one aspect, the invention provides a substantially exfoliatednanocomposite material including starch and hydrophobically modifiedlayered silicate clay.

The hydrophobically modified layered silicate clay (hereinafter“hydrophobic clay”) is present preferably in an amount of 0.1% to 5%w/w, more preferably 0.1% to 3%, and most preferably 0.5% to 2%.

Preferred clays which include such long chain alkyl ammonium ionsinclude CLOISITE™ 20A and CLOISITE™ 25A.

Preferably, the nanocomposite material includes one or moreplasticisers, and/or one or more water-soluble polymers such as but notlimited to polyvinyl alcohol, and/or one or more processing aids.

The starch may be blended with other suitable polymers includingpolyvinyl alcohol and polyesters such as polylactide andpolycaprolactone. The blends used may be modified according to thefunctional and mechanical properties required.

The nanocomposite material preferably has water content of between 5%and 30% by weight, more preferably 5% to 15%, and most preferably 8% to12%.

The nanocomposite material may be used, for example, as rigidthermoplastic packaging trays, injection moulded products such asbottles, flexible films and barrier films, and biomaterials. Thus inanother aspect, the invention provides packaging made from materialincluding the substantially exfoliated nanocomposite material describedabove.

The nanocomposite material has improved mechanical and rheologicalproperties and reduced sensitivity to moisture in that the rates ofmoisture update and/or loss are reduced. The nanocomposite material hasa higher melt strength which facilitates its use in processes such asfoaming or film blowing, and has improved aging characteristics andreduced gas and water permeability.

The improved properties of the nanocomposite material reduce the needfor plasticisers and/or processing aids. In particular, as thenanocomposite material of the invention is more plastic than othermaterials previously disclosed, the amount of plasticiser added may bereduced.

The nanocomposite material has improved clarity, which is an indicationof exfoliation. The material becomes transparent during the preparationprocess, and its level of transparency continues to increase afterpreparation on drying to the desired moisture content. The materialremains transparent for an extended time because it has a reduced rateof retrogradation.

In another aspect, the invention provides a process for preparing thesubstantially exfoliated nanocomposite material described above,including a step of mixing the starch in the form of an aqueous gel withthe hydrophobic clay in a melt mixing device. Suitable melt mixingdevices include extruders. Preferably, the clay is in the form of apowder.

In a further aspect, the invention provides a process for preparing thesubstantially exfoliated nanocomposite material, including the steps ofmixing the starch with the hydrophobic clay to form a masterbatch(hereinafter “the masterbatch process”) and mixing the masterbatch withfurther starch. The masterbatch is collected as strand and may be driedand pelletized for use in further processing. Preferably the masterbatchis mixed with further starch in a second and subsequent step. The secondstep can be performed immediately following the first step or after aperiod of time. The period of time of time between the first and secondsteps is preferably less than three months, and more preferably lessthan two months.

Preferably, the masterbatch process includes a step of rehydrating themasterbatch before the subsequent step of mixing the masterbatch withfurther starch.

Preferably, the masterbatch process includes a step of grinding and/ormilling the resulting masterbatch to a powder before the subsequent stepof mixing the masterbatch with further starch.

More generally, the invention provides a process for preparing ananocomposite material, including a step of mixing starch with clay toform a masterbatch and a subsequent step of mixing the masterbatch withfurther starch. Preferably, the clay is present in the masterbatch in anamount of between 5% and 70% by weight.

The inclusion of a masterbatch in the process has a number ofadvantages. The masterbatch concentrate is easy to handle and store, andmay be fed into an extruder more easily than a raw clay or a clayslurry. The use of a masterbatch also reduces potential for exposure ofthe operator to nanoclay dust during the subsequent step. Themasterbatch may be stored for more than three months, and potentiallyindefinitely, in a relatively dry state with moisture content of lessthan 15% by weight, to be rehydrated before use. Most notably, themasterbatch process leads to improved exfoliation when compared with onestep preparation.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a schematic representation of one suitable extruder which maybe employed in the inventive process.

FIG. 2 is a reference wide angle X-ray scattering (WAXS) graph ofCLOISITE™ 20A according to Examples 30 to 36.

FIG. 3 is WAXS patterns for R1 and of the 1% and 2% CLOISITE™ 20Ananocomposites according to Examples 30 to 36.

FIG. 4 is WAXS patterns for the 3% and 5% CLOISITE™ 20A nanocompositesaccording to Examples 30 to 36.

FIG. 5 is a thermograph of CLOISITE™ 20A according to Examples 30 to 36.

FIGS. 6A and 6B are thermogravimetric derivative mass curves for R1 andCLOISITE™ 20A nanocomposites according to Examples 30 to 36.

FIG. 7 is a transmission electron microscopy (TEM) micrograph of 2%CLOISITE™ 20A according to Example 53 at 50K magnification.

FIG. 8 is a TEM micrograph of 2% CLOISITE™ 25A according to Example 54at 50K magnification.

FIG. 9 is a TEM micrograph of 2% CLOISITE™ Na⁺ according to Example 55at 50 K magnification.

FIG. 10 is a TEM micrograph of 2% CLOISITE™ 20A according to Example 53at 115 K magnification.

FIG. 11 is a TEM micrograph of 2% CLOISITE™ 25A according to Example 54at 115 K magnification.

FIG. 12 is a TEM micrograph of 2% CLOISITE™ CLOISITE™ Na⁺ according toExample 55 at 115 K magnification.

FIG. 13 is WAXS patterns for 2% CLOISITE™ 20A nanocomposites accordingto Examples 56 to 60.

DETAILED DESCRIPTION

In its simplest form, the substantially exfoliated nanocompositematerial of the invention consists only of starch and hydrophobic clay.As would be appreciated by formulators in the art, a raft of additionalcompounds may be added during preparation of the nanocomposite material,including plasticisers and processing aids.

When used in the present specification, “substantially exfoliated”nanocomposite material means a material in which a majority of clayagglomerates are disrupted to tactoids and individual clay layers.Preferably, said tactoids have dimensions that are less than thewavelength of visible light such that the material appears transparentand has few visibly discernable clay particles. More preferably saidtactoids comprise between 2 to 10 clay layers and have a lateraldimension of between 100 and 300 nm.

When used in the present specification, “clay” is a synthetic or naturallayered silicate capable of being exfoliated into nanoparticles.Preferred clays include montmorillonite, bentonite, beidelite, mica,hectorite, saponite, nontronite, sauconite, vermiculite, ledikite,magadite, kenyaite, stevensite, volkonskoite or a mixture thereof.

A “hydrophobically modified layered silicate clay” or “hydrophobic clay”is preferably a clay modified by exchange with a surfactant comprisinglong chain alkyl groups such as a long chain alkylammonium ion, forexample, mono- or di-C₁₂-C₂₂ alkylammonium ion, wherein polarsubstituents such as hydroxyl or carboxyl are not attached to the longchain alkyl. Examples of suitable clays include CLOISITE™ 20A orCLOISITE™ 25A from Southern Clay Industries. The long chainalkylammonium ion in CLOISITE™ 20A is depicted in Formula 1 and that inCLOISITE™ 25A is depicted in Formula 2.

-   -   Where HT is Hydrogenated Tallow (˜65% C18; ˜30% C16; ˜5% C14)

Anion: Chloride

Formula 1: Long Chain Alkylammonium Ion in CLOISITE™ 20A

-   -   Where HT is Hydrogenated Tallow (˜65% C18; ˜30% C16; ˜5% C14)

Anion: Methyl Sulfate

Formula 2: Long Chain Alkylammonium Ion in CLOISITE™ 25A

The surfactant in CLOISITE™ 20A includes two hydrophobic hydrogenatedtallow long chains, and does not include polar substituents such ashydroxyl or carboxyl. That in CLOISITE™ 25A includes one hydrophobichydrogenated tallow long chain, and a second chain which is six carbonatoms in length. Again, the modifier does not include hydroxyl orcarboxyl substituents.

Examples of unsuitable surfactants include CLOISITE™ Na⁺ and CLOISITE™30B, which is depicted in Formula 3.

-   -   Where T is Tallow (˜65% C18; ˜30% C16; ˜5% C14)

Anion: Chloride

Formula 3: CLOISITE™ 30B

CLOISITE™ 30B is unsuitable as it has polar hydroxyl groups. CLOISITE™Na is unsuitable as it does not include any long chain alkyl organicmodifiers.

Other modifying agents such as suitable phosphonium ion or suitablenon-ionic surfactants may also be used.

The hydrophobic clay may be preformed or may be formed in situ duringproduction of the nanocomposite or nanocomposite masterbatch fromunmodified clay and the modifying agent.

The starch may be a natural or derivatized starch such as corn (maize)starch, potato starch, tapioca starch, wheat starch, rice starch,cassava starch, arrowroot starch or sago starch. Starch consists ofamylopectin, amylose and other minor components. High amylose starch ispreferred, although low amylose starch may also be employed. Derivatizedstarches include esters such as acetylated starch or starch succinate,or carboxymethylated starch, and ethers, such as hydroxyalkylatedstarch, preferably hydroxypropylated starch. Derivatised starches may beformed as the reaction product of starch with epoxides, cyclic lactones,cyclic carbonates, cyclic and acyclic anhydrides. A high amylosehydroxypropylated starch such as one having an amylose level above 50%,for example GELOSE™ A939 (Penford) or ECOFILM™ (National Starch &Chemical Company) or equivalent starch is preferred. The mostappropriate starch is to be selected based on the properties required ofthe product and its processability. The starch is present preferably inan amount of 5% to 99% by weight.

Although the water present by virtue of the starch may act as aplasticiser, any other suitable hydrophobic or hydrophilic plasticisermay also be introduced into the process if required. Suitableplasticisers include polyols and may be one or more of poly(vinylalcohol) (such as ELVANOL™), sorbitol, maltitol, glycerol, mannitol,xylitol, erythritol, ethylene glycol and diethylene glycol.

Suitable processing aids include C₁₂-C₂₂ fatty acids and their saltssuch as stearic acid, calcium stearate, sodium stearate, palmitic acidand lauric acid.

The process of naocomposite material formation can be performed bydirect addition of the hydrophobic clay as a dry powder, as a powdermoistened with water or a plasticiser, as an aqueous slurry or as astarch based masterbatch. Preferably, the process of nanocompositematerial formation is performed as a masterbatch process. Firstly, astarch clay masterbatch containing 5% to 70% by weight clay is preparedby mixing the starch, the hydrophobic clay, one or more plasticisers andoptionally one or more processing aids or other components.

The masterbatch is collected as strand and may be dried and pelletizedfor use in the second step. If the masterbatch is to be stored for along period it is preferred to have a low water content, preferablybetween 5% and 15% by weight. The masterbatch is rehydrated by additionof water and equilibrated to have a water content which is preferablybetween 15% and 30%, more preferably between 20% and 30% by weight.

Subsequently, a nanocomposite material containing 0.1% to 5% clay byweight is prepared by mixing the masterbatch with further starch andoptionally plasticisers and processing aids.

The materials may be extruded. Preferred conditions for the extrusionare a maximum temperature of between 120 and 140° C. and pressure ofbetween 1 and 4 atmospheres.

The process includes premixing the modified starch, clay, or claymasterbatch, and any other dry components to produce a mixture. This canbe carried out in any conventional mixer. The mixture can be introducedinto a screw extruder and subjected to elevated temperatures by theshearing action of the screw and the application of external heat to thebarrel. The temperature can be raised to a range of about 120° C. toabout 180° C. The material is best manufactured by means of extrusioncompounding, using co- or counter-rotating twin screw or selected designsingle screw extruders. Twin screw co-rotating compounding, with anextrusion pressure of at least about 5 or about 10 bar (1 bar=100 kPa)and with a screw speed of at least about 80 rpm or about 100 rpm.

Water can be introduced substantially simultaneously with the start ofextrusion such as in the initial barrel sections by means of liquidinjection for “gelatinising” (also referred to as destructurising,cooking, or melting) the starch into a polymeric gel structure. Starchwas cooked by the combined action of water, elevated temperature andshear provided by the screw. Water may also serve to dissolve any otherwater soluble polymers added, such as poly(vinyl alcohol) and to act asa plasticiser in the end-product thereby softening the material andreducing the modulus and brittleness. The melt and/or destructurisedstarch nanocomposite blend can then be propelled toward the die and inmoving forward the temperature can be reduced to prevent foaming withoutthe need for venting. Alternatively, a foaming agent may be added to thecombination during the process. Water may be added to a calculatedconcentration of about 10% to 50% by weight, preferably about 20% to 40%by weight, more preferably about 22% to about 40% by weight, or evenmore preferably about 25% to about 35% by weight of the total mixture oranother mixture. During and following cooking of the starch the extruderserves to mix and homogenize the nanocomposite composition. A typicalresidence time in the extruder is between 1 and 2.5 min, depending ontemperature profile and screw speed.

Whilst not intending to be bound by theory, it is speculated thatmodifying the clay so that it becomes hydrophobic may enable the clayparticles to come apart more easily. This may result in the high levelof exfoliation observed in the resulting nanocomposite material.

EXAMPLES

Materials

CLOISITE™ 20A, a natural montmorillonite modified by dimethyldi(hydrogenated tallow) quaternary ammonium chloride from Southern ClayIndustries

CLOISITE™ 25A, a natural montmorillonite modified by dimethyl2-ethylhexyl (hydrogenated tallow) ammonium methylsulfate from SouthernClay Industries

CLOISITE™ 93A, a natural montmorillonite modified with methyldi(hydrogenated tallow) ammonium bisulfate from Southern Clay Industries

GELOSE™ A939, a high amylose corn starch, GELOSE™ 80, with a quotedamylose content of ˜80%, modified by reaction with propylene oxide toform 6.5% hydroxypropyl substitution (w/w). GELOSE™ A939 was obtainedfrom Penford, Australia

ECOFILM™, high amylose corn starch, NYLON™ VII, with a quoted amylosecontent of ˜70%, modified by reaction with propylene oxide to give 6.5%hydroxypropyl residues (w/w). It was obtained from National Starch andChemical Company

Poly(vinyl alcohol), ELVANOL™ from Dupont

Stearic acid, PALMERA™ from Palm-Oleo BHD

Equipment

A twin screw extruder including ten temperature controlled barrel zones,three unheated zones, and a cooled feed block was used for clay-starchmasterbatch preparation. Materials were fed into the extruder via agravimetric feeder. The extruder was operated in co-rotating(intermeshing self wiping) mode. The melt temperature was monitored atthree positions along the barrel and in the die. A schematicrepresentation of one suitable extruder is shown in FIG. 1.

Starch and clay were fed into the barrel through the hopper at C1. Waterwas injected into the barrel through a liquid pump at C4. Temperaturezones from C5 to C9 are cooking zones and full gelatinization should becompleted in these zones. Die or sheet die is after C11. The temperatureprofiles with ten heating zones and die were controlled as follows:

TABLE 1 Temperature profiles of extrusion Die Sheet die Temperaturetemperature temperature Starch type profiles (° C.) (° C.) (° C.) ForGELOSE ™ 60, 80, 90, 110, 120, 80 A939 120, 115, 110, 75, 80 masterbatchFor GELOSE ™ 60, 80, 90, 120, 130, 80 90 A939 2^(nd) 130, 130, 120, 110,extrusion 80

The proportions quoted in the following tables are weight percentage.They are not dry weights. They include the moisture contained in thematerials. The typical moisture content of GELOSE™ A939 is 11% (w/w).

Processing of clay-starch masterbatch was carried out in a laboratoryscale co-rotating twin screw extruder. The general screw geometry was:diameter 27 mm, L/D ratio 48, and maximum rotation speed 1200 rpm.Materials were fed into the extruder via a gravimetric feeder. In theextruder, the materials went through convey, water, blend, compress,mix, convey, mix, compress, mix, convey, and compress stages. The melttemperature was monitored at three positions along the barrel and in thedie. The temperature profiles were controlled as follows:

TABLE 2 Temperature profiles of sheet extrusion from clay-starchmasterbatch Sheet die Material Temperature profiles (° C.) temperature(° C.) Clay-starch 40, 70, 80, 90, 95, 120, 140, 150, 105, 100, 105masterbatch 150, 140, 120, 100, Control 1 40, 70, 80, 90, 95, 120, 140,150, 105, 100, 105 (without clay- 150, 140, 120, 100, starchmasterbatch) Control 2 40, 70, 80, 90, 95, 120, 130, 135, 105, 100, 105(without clay- 135, 130, 120, 100, starch masterbatch)

Trays were thermoformed from sheet produced from the range offormulations by using a contact heat thermoforming machine. The keythermoforming conditions were: heating time 1 s, heat vent time 0.5 s,form time 1 s, form vent time 0.4 s, thermoforming temperature 125° C.,and mould heat temperature 21° C.

The following examples demonstrate processes for production ofmasterbatches and of nanocomposites formed using said masterbatchesaccording to the invention.

Examples 1 and 2

The examples tabulated in Table 3 demonstrate clay-starch masterbatchpreparation.

The following procedure is typical:

Preparation of 10% Clay Masterbatch (CLOISITET™ 25A)

GELOSE™ A939 (16.2 kg), PVOH (1.62 kg), stearic acid (180 g) andCLOISITE™ 25A (2 kg) were combined in a tumble mixer for 2 h. The mixedpowder was fed to the main feed hopper of the extruder via a gravimetricfeeder through an auger at rate of 3.5 kg/h. The temperature profile wasset as shown in Table 1. Water was injected into the barrel through aliquid pump at a flow rate of 26 g/min. The screw speed was 162 rpm. Theextrudate strand was collected, air-dried overnight and pelletized.

TABLE 3 Preparation of the masterbatch Clay GELOSE ™ PVOH Stearic acidExample Clay type (%) A939 (%) (%) (%) 1 CLOISITE ™ 10.00 81.00 8.100.90 25A 2 CLOISITE ™ 10.00 81.00 8.10 0.90 20A

Examples 3 to 5

The examples tabulated in Table 4 demonstrate the preparation of starchnanocomposite sheet (2% CLOISITE™ 25A) from 10% clay masterbatch Thefollowing procedure is typical:

A starch mixture was prepared comprising GELOSE™ A939 (9 kg), PVOH (0.9kg) stearic acid (0.1 kg) and mixed in the tumble mixer for 2 h. The drymasterbatch pellets (from Example 1 above) were hydrated (the water wasadded into the mixer at a flow rate of 2 mL/min) in a tumble mixerovernight to achieve a final water content of approximately 26%. Thetemperature profile was set as shown in Table 1 for the 2^(nd)extrusion. The screw speed was 162 rpm. The starch mixture was fed via agravimetric feeder to the main hopper at a rate of 2.8 kg/h. Thehydrated masterbatch pellets were fed via a second gravimetric feeder tothe main hopper at a rate of 700 g/h. Water was injected at a flow rateof 26 g/min. The extrudate sheet was collected, air-dried for 2 h,rolled and stored in plastic bags.

TABLE 4 Preparation of starch composite sheet Masterbatch Finalcomposition example GELOSE ™ Stearic (feed rate - A939 PVOH acid ExampleClay type g/h) Clay (%) (%) (%) (%) control none — (1750) 0 90 9 1 3CLOISITE ™ 1 (350) 1.00 89.10 8.91 0.99 25A 4 CLOISITE ™ 1 (700) 2.0088.20 8.82 0.98 25A 5 CLOISITE ™  1 (1750) 5.00 85.50 8.55 0.95 25A

Total feed rate (starch mixture+masterbatch) 3.5 kg/h

The examples prepared with hydrophobic clays possessed exceptionalclarity and substantially higher melt strength compared to a controlwithout CLOISITE™. This improvement in properties was most marked forcomposites prepared with the more hydrophobic CLOISITE™ 25A

Examples 6 to 8

The examples tabulated in Table 5 demonstrate clay-starch masterbatchpreparation.

Procedures of Starch Composite Preparation (CLOISITE™ 20A)

Preparation of 10% CLOISITE™ 20A Masterbatch

The following procedure is typical:

GELOSE™ A939 (16.2 kg), PVOH (1.62 kg), stearic acid (180 g) were mixedin a mixer for 2 h. The mixed powder was fed into barrel via agravimetric feeder through hopper at rate of 3.15 kg/h. CLOISITE™ 20Awas fed into barrel through hopper at a flow rate of 350 g/h. Thetemperature profile was set as shown in Table 1 for master batch. Waterwas injected into the barrel through a liquid pump at a flow rate of 26g/min. The screw speed was 162 rpm. The extrudate strings werecollected, air-dried overnight and pelletized.

Plasticisers such as sorbitol, erythritol and xylitol may be added tothe powder before the powder was fed into the barrel.

TABLE 5 Preparation of masterbatch Clay GELOSE ™ PVOH Stearic acidExample Clay type (%) A939 (%) (%) (%) 6 CLOISITE ™ 5.00 85.50 8.55 0.9525A 7 CLOISITE ™ 5.00 85.50 8.55 0.95 93A 8 CLOISITE ™ 5.00 85.50 8.550.95 20A

Examples 9 to 15

The examples in Table 6 demonstrate preparation of starch compositesheet from 5% clay masterbatch.

The dry masterbatch pellets were hydrated in a mixer overnight toachieve a water content of approximately 26%. Water was added into themixer at a flow rate of 2 ml/min. The mixed powder was fed into thebarrel via a gravimetric feeder through the hopper at rate of 2.8 kg/h.The hydrated masterbatch pellets were fed into barrel via a feeder at arate of 700 g/h. The temperature profile was set as shown in Table 1 forthe 2^(nd) extrusion. Water was injected into the barrel through aliquid pump at a flow rate of 27 g/min. The screw speed was 162 rpm. Theextrudate sheets were collected, air-dried for 2 h, rolled into a coiland stored.

TABLE 6 Preparation of starch composites Final composition GELOSE ™Stearic Masterbatch A939 PVOH acid Example Clay type entry Clay (%) (%)(%) (%) 9 CLOISITE ™ 2 1.00 89.10 8.91 0.99 25A 10 CLOISITE ™ 2 5.0085.50 8.55 0.95 25A 11 CLOISITE ™ 4 1.00 89.10 8.91 0.99 93A 12CLOISITE ™ 4 2.00 88.20 8.82 0.98 93A 13 CLOISITE ™ 5 0.50 89.55 8.9550.995 20A 14 CLOISITE ™ 5 1.00 89.10 8.91 0.99 20A 15 CLOISITE ™ 5 2.0088.20 8.82 0.98 20A

The examples prepared with clays possessed exceptional clarity andsubstantially higher melt strength with respect to a control withoutCLOISITE™. This improvement in properties was most marked for samplesprepared with the more hydrophobic clays CLOISITE™ 20A and CLOISITE™25A.

Examples 16 to 17

The examples demonstrate 50% clay-starch masterbatch preparation and aretabulated in Table 7.

The following procedure is typical:

Procedures of Starch Composite Preparation (CLOISITE™ 25A)

GELOSE™ A939 (9.0 kg), PVOH (0.9 kg), stearic acid (100 g) and CLOISITE™25A (10.0 kg) were mixed for 2 h in rotary mixer. The mixed powder wasfed into a barrel via a gravimetric feeder at rate of 3.5 kg/h. Thetemperature profile was set as shown in Table 1 for the masterbatch.Water was injected into the barrel through a liquid pump at a flow rateof 25 g/min. The screw speed was 162 rpm. The extrudate strand wascollected, air-dried overnight and pelletized.

TABLE 7 Preparation of the 50% clay masterbatch Clay GELOSE ™ PVOHStearic acid Example Clay type (kg) A939 (kg) (kg) (%) 16 CLOISITE ™10.00 9.00 0.90 0.10 25A 17 CLOISITE ™ 10.00 9.00 0.90 0.10 20A

Examples 18 to 29: Comparative Transparency of CLOISITE™ Na andCLOISITE™ 20A

TABLE 8 Formulation R1 Composition % · w/w GELOSE ™ A939 starch(including 12% moisture) 90.0 PVOH (ELVANOL ™) 9.0 Stearic acid 1.0TOTAL DRY MIX 100.0

The formulation R1 is a composite which does not include a nanoclay andis used for comparative purposes in these examples.

As discussed in the Detailed Description, CLOISITE™ 20A is significantlymore hydrophobic than CLOISITE™ Na.

Examples 18 to 29 demonstrate that formulations including thehydrophobically modified layered silicate clay CLOISITE™ 20A aresignificantly more transparent than formulations including either themore hydrophilic clay CLOISITE™ Na or that containing no clay.

UV-visible spectra were obtained over wavelength range of 800 to 200 nmat 1008 nm·min⁻¹. Transmittance was recorded and related to absorbanceby the equation A=−log(T). Transparency was calculated based on thetransmitted light from 350 to 800 nm and divided by 100% transmittedlight. Optical absorbance coefficient (OAC) was determined bynormalisation of specimen thickness. The OAC was compared with R1produced on the same day (or series) as the composites. The relativechanges are listed in Table 9.

TABLE 9 UV-visible Transparency and comparison to R1 produced on thesame day. Example Clay Transparency Optical Absorbance Composition typeClay (%) (%) Coefficient (m⁻¹) 18 Na 1 67.78 614 19 — 71.79 543 20 Na 270.56 571 21 Na f 3 66.94 709 22 Na c 3 67.41 772 23 Na 5 68.11 641 2420A 1 84.41 260 25 20A 2 83.92 304 26 20A f 3 82.68 306 27 — 77.83 39428 20A c 3 84.03 308 29 20A 5 83.32 288 f = masterbatch was fed directlyto the extruder using feeder 2; c = starch and masterbatch were blendedin a concrete mixer before being fed into the extruder.CLOISITE™ Na

All of the CLOISITE™ Na nanocomposites showed an increased OACindicating a reduced transparency compared with the R1 made on same day.The OAC of R1 was 543 m⁻¹. Inclusion of 1% CLOISITE™ Na resulted in OACof 614 m⁻¹, an increase in OAC, therefore a reduction in transparency.

The OAC was increased up to 42% with 3% CLOISITE™ Na concrete mixermethod, in the worst case. The 3% CLOISITE™ Na feeder and 5% CLOISITE™Na faired similarly in OAC. The 2% CLOISITE™ Na showed lower OACcompared with the concrete mixer preparation, 5% higher than R1.

CLOISITE™ 20A

Remarkable improvements in transparency, as indicated by reduction inOAC were observed across all compositions when compared with the R1control made on same day. The OAC of R1 listed in Table 9 was 394 m⁻¹.Improvements of at least 21 to 49% in OAC reduction have been obtainedfor CLOISITE™ 20A nanocomposites. The most transparent were 1 and 5%CLOISITE™ 20A with OAC of 260 m⁻¹ and 288 m⁻¹, respectively. Addition of2-3% CLOISITE™ 20A exhibited similar OAC between 300 to 310 m⁻¹. Of the3% CLOISITE™ 20A nanocomposite, the concrete mixer method providedbetter consistency and lower variability in the measured transparency.This may be attributed to a more homogeneous input into the extruder.

Discussion

The introduction of CLOISITE™ Na resulted in a reduction in transparencyand an apparent yellowness observed in the sheet materials. Conversely,the inclusion of CLOISITE™ 20A in amounts of up to about 5% provedbeneficial in increasing the transparency of the sheet. The improvementwas most significant with 1 to 2% CLOISITE™ 20A.

Examples 30 to 36: Mechanical Tensile Properties of CLOISITE™ 20A

The mechanical tensile experiments demonstrate that the addition ofCLOISITE™ 20A improves mechanical tensile properties of sheet material.

Sheets were cut into strip (25×200 mm²). Four thickness measurementswere made for each strip. Mechanical tensile tests were conductedaccording to ASTMD882. The extension rate of 10 mm·min⁻¹ was used with a2 kN load cell. The thermoplastic composites were conditioned for 48 hat 50% and 25% relative humidity prior to testing. The average specimenthickness was 250 μm. Statistical analysis was performed for minimum ofn=10 replicate specimens per composite. Tensile tests of thermoplasticstarch films were conducted both in machine direction (MD) andtransverse to the direction of extrusion (TD). The results are shown inTable 10.

TABLE 10 Summary of Elongation break of sheets as affected by relativehumidity with reference to extrusion direction. Ratio of Elongationbreak values Machine/ 50% transverse 50% RH/25% RH RH/25% RH Sheets (50%RH) (machine) (transverse) Example 30 - R1 6.27 2.95 2.52 Example 31 -R1, 1% 20A 1.96 2.58 2.43 Example 32 - R1, 2% 20A 1.54 2.27 1.97 Example33 - R1, 3% 20A, 1.69 2.19 1.58 Feeder Example 33 - R1 4.59 3.04 2.37Example 34 - R1, 3% 20A 1.09 2.25 1.72 concrete mix Example 35 - R1, 5%20A 0.90 1.67 1.81 concrete mix

When relative humidity of the environment decreased from 50% to 25%,significant increases were found in the E-modulus values and Fmax valuesof both CLOISITE™ 20A sheets and R1 sheet, due to the loss ofplasticizing water, whereas significant decrease in elongation breakvalues were found in all sheets.

Adding CLOISITE™ 20A provided a more isotropic sheet as indicated by theelongation at break being similar in the machine and transversedirections. For example, for R1 the ratio of elongation break value inthe machine direction to that in the transverse direction was 5-6,whereas ratios for the CLOISITE™ 20A nanocomposite sheet were between1-2 (Table 10).

Adding CLOISITE™ 20A slightly improved mechanical performance tolerancewith change in humidity from 50% RH and 25% RH (Table 10). In themachine direction, ratio of elongation break value for R1 at 50% RH to25% RH was 3, whereas ratios for the composite sheet was between1.67-2.58. In the transverse direction, ratio of elongation break valuefor R1 at 50% RH to 25% RH was 2.37-2.52, whereas ratios for thecomposite sheet were between 1.58-2.43.

Examples 30 to 36: WAXS of CLOISITE™ 20A

The WAXS experiments demonstrate that the formulations including 1% or2% CLOISITE™ 20A were substantially exfoliated.

The reference WAXS pattern for CLOISITE™ 20A is shown in FIG. 2. FIG. 3shows the WAXS patterns for R1 and of the 1% and 2% CLOISITE™ 20Ananocomposites. They show no peaks due to clay and indicate anexfoliated structure was obtained. FIG. 4 shows patterns for the 3% and5% nanocomposites. The WAXS pattern obtained for the 3% CLOISITE™ 20A(concrete) nanocomposite suggests a high degree of exfoliation as noclay peaks were observed. The 3% CLOISITE™ 20A (feeder) and 5% CLOISITE™20A nanocomposites show a small peak at 2θ of 4.6° This suggests thatthe concrete method gave greater exfoliation of the clay.

Examples 30 to 36: Thermogravimetry of CLOISITE™ 20A

The thermogravimetry experiments demonstrate that formulations withCLOISITE™ 20A have high thermal stability and low mass loss rates.

FIG. 5 provides a thermogram of CLOISITE™ 20A. Three mass loss stagesoccurred, the first at ˜38° C., main degradation at 315° C., followed bya broad loss at 629° C. Mass losses can be attributed to water lossesand addition degradation of organic modifier.

FIG. 6A and FIG. 6B show the thermogravimetric derivative mass curvesfor R1 and CLOISITE™ 20A nanocomposites. Table 11 lists extracted datafor the sheets. R1 made on the two different days showed somedifferences in the thermogram, mainly in the third decomposition step.The 1% and 2% CLOISITE™ 20A slowed the mass loss rates in all the stepsas listed in Table 11.

Composite 3% concrete seemed to show higher mass loss rates in alldecomposition steps compared with 3% feeder nanocomposite. The 5%nanocomposite exhibited higher thermal stability and generally lowerrates of mass loss compared to other nanocomposites and R1.

Composite 2% CLOISITE™ 20A seemed to show optimal properties; ie, lowmass loss rates (broader peak in derivative curve), and higher thermalstability than R1.

TABLE 11 Thermogravimetric mass loss, rate and temperature data Clay inMass Mass loss Mass loss Mass loss composite remain (temp, rate (temp,rate (temp, rate Composition (%) i (%) % · min⁻¹) % · min⁻¹) % · min⁻¹)CLOISITE ™ 62.5  1.0 (38.5, 0.39) 24.0 (315, 4.2)  13.0 (629, 1.5)  20A070417-1 0 0.73 10.8 (70.2, 2.2) 68.3 (353, 51.4) 19.5 (479, 16.4)070417-2 1 1.74  11.1 (73.1, 2.05) 67.9 (360, 40.5) 18.9 (497, 13.9)070417-3 0 0.49 10.9 (69.5, 2.2) 68.2 (355, 49.6) 18.8 (490, 15.9)070417-4 2 1.59 10.8 (70.2, 1.9) 69.3 (357, 40.9) 18.0 (493, 15.4)070417-5 3 f 2.08 10.9 (71.5, 2.1) 68.2 (352, 44.3) 17.0 (488, 13.6)070417-6 3 c 1.99 11.3 (68.8, 2.0) 68.0 (344, 47.4) 17.2 (485, 14.9)070417-7 5 3.13 10.9 (76.2, 1.9) 66.8 (357, 45.3) 16.7 (486, 10.6)

Examples 37 to 43: Processing, Thermoforming and Drop Test of CLOISITE™20A

Examples 37 to 43 demonstrate that trays including CLOISITE™ 20A wereclearer having significantly better drop test performance.

Master batch pellets were ground into powder. The following sheets wereextruded:

Example 37—R1

Example 38—R1, 1%20A

Example 39—R1, 2%20A

Example 40—R1, 3%20A (masterbatch added by feeder 2)

Example 41—R1

Example 42—R1, 3%20A (masterbatch mixed with starch in concrete mixer)

Example 43—R1, 5%20A.

The formulation of each sheet is summarised in Table 12.

TABLE 12 The formulations of CLOISITE ™ 20A sheets Product Eg 37 Eg 38Eg 39 Eg 40 Eg 41 Eg 42 Eg 43 Supplier Batch (kg) (kg) (kg) (kg) (kg)(kg) (kg) Penford A939 10.197 10.197 10.197 10.197 10.197 10.197 7.05(C7317- 09) DuPont PVOH 0.9 0.9 0.9 0.9 0.9 0.9 0.62 71-30 Acid- Stearic0.06 0.06 0.06 0.06 0.06 0.06 0.04 Chem Acid International Clay 20AMB0.22 0.46 0.72 0.72 0.88 Clositie

All nanocomposite sheets and R1 sheets were extruded at a temperaturearound 130° C. The processing conditions are summarized in Table 13.

TABLE 13 Example 37 to 43 processing conditions Example No. Barrel Temp(° C.) 37 35, 70, 80, 90, 95, 130, 135, 135, 130, 120 38 35, 70, 80, 90,95, 130, 135, 135, 130, 120 39 35, 70, 80, 90, 95, 130, 135, 135, 130,120 40 40, 70, 80, 90, 95, 130, 135, 135, 130, 120 41 35, 70, 80, 90,95, 130, 135, 135, 130, 120 42 35, 70, 80, 90, 95, 130, 135, 135, 130,120 43 35, 70, 80, 90, 95, 130, 135, 135, 130, 120

The output rate for each example was 7 to 15 kg/h, and the extruderspeed for each example was 450 rpm.

Thermoforming of Trays

Trays were thermoformed from sheet about 250 μm (0.25 mm) thick intochocolate trays of 13.5×13.5 cm using a thermoforming machine. The keythermoforming conditions were: heating time 1 s, heat vent time 0.5 s,form time 1 s, form vent time 0.4 s, thermoforming temperature 125° C.,and mould heat temperature 21° C.

All CLOISITE™ 20A sheets had similar thermoforming properties to R1control. Trays made from CLOISITE™ 20A sheets were clearer than traysmade from R1 control.

Drop Test

For drop tests, the tray cavities were filled with moulded plasticpieces corresponding to the weight of chocolate pieces totaling 125 gand the filled tray, packaged in a secondary carton package, was letdrop from a height of either 0.9 m or 1.5 m, depending on the relativehumidity conditions. Drop tests at 50%·RH (and 23° C.) were carried outfrom a height of 1.5 m, while at 35%·RH the packed trays were droppedfrom a height of 0.9 m. A total of 10 trays were dropped for each trial.The damaged trays were rated thereafter, according to the followingscale and definitions, where each tray is fitted into the highestnumbered (worst performing) category applicable.

In Table 14 below, crack denoted running from the edge or inside thetray; chip was a piece missing from the edge of the tray; the size wasthe maximum dimension of the missing portion, not including anyassociated crack; hole occurred in the middle of a tray; and separatedpiece was a large piece that was 75% or more detached from the tray.

TABLE 14 Damaged tray rating scale Defects Number Crack size Chip sizeTotal allowable Category (mm) (mm) Hole size (mm) defects 0 0 0 0 0 1≦10 ≦5 0 ≦2 2 ≦30 ≦20 ≦10 ≦4 3 ≦30 ≦20 ≦10 ≦6 4 >30 >20 >10 ≦45 >30 >20 >10 >4, or ≧1 separated piece

TABLE 15 Drop test results of trays thermoformed from CLOISITE ™ 20Asheets and R1 sheet 1^(st) Drop 1.1 m @ 2^(nd) Drop 1.3 m @ 3^(rd) Drop1.3 m @ Example machine direction machine direction Transverse direction37 3 out of 10 trays failed 3 more trays failed (2 2 more trays failed(1 (small piece fallen off) piece fallen off edge & bridge break and 1 1minor bridge break) piece fallen off edge) 38 All passed All passed 1tray failed (small piece fallen off) 39 All passed All passed All passed40 1 out of 10 trays failed All passed All passed (small piece fallenoff) 41 8 out of 20 trays failed 5 more trays failed (4x 2 more traysfailed (2x large pieces fallen small piece fallen off (1x small piecefallen off edge, 6x small edge, 1x large piece off edge, 1x large piecepieces off edge) fallen off edge) fallen off edge) 42 All passed Allpassed All passed 43 All passed All passed All passed

As shown in Table 15, all trays made from CLOISITE™ 20A sheets hadsignificantly better drop test performance than R1. For R1, 75%-80%trays failed the drop tests, whereas all 2% CLOISITE™ 20A, 3% CLOISITE™20A (concrete mix) and 5% CLOISITE™ 20A trays passed the drop test.

Examples 44 to 47: Trial Conducted on Large Production Extruder (ENTEK™103)

Examples 44 to 47 demonstrate that trays including CLOISITE™ 20A areclearer and have significantly better drop test performance.

Master batch pellets were ground into powder. The following sheets wereextruded:

Example 44—R1

Example 45—R1, 2% CLOISITE™ 20A

Example 46—R1, 2% CLOISITE™ 20A

Example 47—R1, 2% CLOISITE™ 20A

The output rate for each example was 210 kg/h, and the extruder screwspeed for each example was 225 rpm.

TABLE 16 Barrel temperatures set on ENTEK ™ 103 Example No. Barrel Temp(° C.) 44 30, 70, 90, 125, 135, 140, 130, 100, 75, 75, 75, 80, 80 45 30,70, 90, 125, 135, 140, 130, 100, 75, 75, 75, 80, 80 46 30, 70, 90, 125,135, 140, 130, 100, 75, 75, 75, 80, 80 47 30, 70, 90, 125, 135, 140,130, 100, 75, 75, 75, 80, 80

TABLE 17 Drop test results on ENTEK ™ 103 composites (50% · RH and 35% ·RH) Drop test at Drop test at Example number Roll number 1.2 m 50% · RH0.9 m at 35% · RH 44 23390 1.5 4.9 45 23391 0 2.9 46 23392 0 4 47 233940 3

TABLE 18 Haze results on ENTEK ™ 103 composites Example number Rollnumber Haze test 44 23390 31.83 45 23391 23.67 46 23392 23.88 47 2339423.29The haze result in the control was higher than normal due to thepresence of Maltese Crosses in the sheet.

Examples 48 to 52: Trial Conducted on Pilot Scale Extruder (ENTEK™ 27)

Examples 48 to 52 demonstrate that trays including CLOISITE™ 20A areclearer and have significantly better drop test performance.

Master batch pellets were ground into powder. The following sheets wereextruded:

Example 48—R1

Example 49—R1, 2% CLOISITE™ 20A added as pure CLOISITE™ 20A (notmasterbatched)

Example 50—R1, 2% CLOISITE™ 20A added as 50% CLOISITE™ 20A masterbatch

Example 51—R1

Example 52—R1, 2% CLOISITE™ 20A added as 25% CLOISITE™ 20A masterbatch

The output rate for each example was 16 kg/h, and the extruder screwspeed for each example was 395 rpm.

TABLE 19 Barrel temperatures set on ENTEK ™ 27 Example No. Barrel Temp(□C.) 48 40, 70, 80, 90, 95, 110, 120, 120, 120, 120, 80, 70 49 40, 70,80, 90, 95, 110, 120, 120, 120, 120, 80, 70 50 40, 70, 80, 90, 95, 110,120, 120, 120, 120, 80, 70 51 40, 70, 80, 90, 95, 110, 120, 120, 120,120, 80, 70 52 40, 70, 80, 90, 95, 110, 120, 120, 120, 120, 80, 70

TABLE 20 Drop test results on ENTEK ™ 27 composites Drop test at 0.9 mExample number Sample description 35% · RH 48 070824-R1 3.8 49 070824-2%20A-pure 2 50 070824-2% 20A-50% master 2.1 51 070828-R1-control 3.5 52070828-2% 20A-25% masterbatch 2

TABLE 21 Haze results on ENTEK ™ 27 composites Example number Rollnumber Haze test 48 070824-R1 13.26 49 070824-2% 20A-pure 8.63 50070824-2% 20A-50% master 8.75 51 070828-R1-control 11.15 52 070828-2%20A-25% masterbatch 6.87

Examples 53 to 55: TEM Analysis

TEM analysis was used in Examples 53 to 55 to demonstrate thesubstantial exfoliation achieved when hydrophobic CLOISITE™ 20A orCLOISITE™ 25A is used, and the degree of exfoliation is compared withhydrophilic CLOISITE™ Na. In each case, a concentration of 2% CLOISITE™was employed, and the specimens were prepared in accordance with theprocedure outlined in Examples 44 to 47.

FIGS. 7 and 10 relate to CLOISITE™ 20A, FIGS. 8 and 11 relate toCLOISITE™ 25A, and FIGS. 9 and 12 relate to CLOISITE™ Na. In FIGS. 7, 8and 9, the magnification is 50 K and the projected area is 2.58 μm². InFIGS. 10, 11 and 12, the magnification is 115 K and the projected areais 0.48 μm².

The TEM images in FIGS. 7, 8 and 9 were analysed as shown in Table 22.

TABLE 22 Analysis of TEM images in FIGS. 7, 8 and 9 Distribution ofplatelets within specimen: % (actual number of layers) Multiple Double-(4-9) Micro-layer Overall Singular Triple Smaller (10+): Larger numberof (1) (2-3) tactoids tactoids species FIG. 7  52 (100) 26 (51) 22 (42)0 (0) 193 FIG. 8 62 (70) 19 (22) 19 (22) 0 (0) 114 FIG. 9 46 (41) 28(25) 23 (21) 3 (3) 90

Examples 56 to 60: 2% CLOISITE™ 20A Direct Nanocomposite Sheets by WAXS

Examples 56 to 61 the WAXS analysis of powdered 2% CLOISITE™ 20Ananocomposite sheets made that were prepared for a 50% masterbatch or bydirect addition of clay.

FIG. 13 shows WAXS pattern of powdered 2% CLOISITE™ 20A nanocompositesheet prepared from a 50% masterbatch, powdered 2% CLOISITE™ 20Ananocomposite sheet that was prepared by direct addition and CLOISITE™20A. An adapted scale is drawn by 2000 units to each curve. Table 16shows the relevant d-spacing values. All sheets made from directaddition of 2% CLOISITE™ 20A showed expansion of clay platelets due tointercalation of starch between clay platelets in the residual tactoids.The sheet made from 50% CLOISITE™ 20A masterbatch pellets showedgreatest expansion of the clay platelets (d-spacing increased from 23.2Å to 40.5 Å). The 2% 20A CLOISITE™ sheets made by direct addition show asmaller expansion. A possible explanation for the greater expansionobserved for the 2% CLOISITE™ 20A from 50% masterbatch nanocomposite maybe that this materials has been extruded twice. One in forming themasterbatch and again in forming the nanocomposite sheet. The higherrelative crystallinity values (from starch area) were not observed fromnanocomposite sheets. However, all nanocomposite sheets show creation ofV-type and E-type crystal structures.

TABLE 23 WAXS data of extruded 2% CLOISITE ™ 20A nanocomposite sheetsand CLOISITE ™ 20A. d (nm) (2θ°) of unexfoliated Example Composite clay56 CLOISITE ™ 20 (A) 2.35 (3.8°), 1.21 (7.3°) 2% CLOISITE ™ 20Ananocomposites (FIG. 13) 57 2% 20A_from 50% 20A 4.05 (2.2°) [5.08,3.54], 1.96 masterbatch (B) (4.5°) 58 2% 20A_direct (C) 3.74 (2.4°)[5.14, 3.44], 1.96 (4.5°) 59 2% 20A_direct (D) 3.42 (2.6°), 1.97 (4.5°)60 2% 20A_direct (E) 3.32 (2.7°), 19.2 (4.6°)

Example 61: 10% CLOISITE™ 25A in R1

A procedure for the preparation of nanocomposite sheets based on a 10%

CLOISITE™ 25A masterbatch in R1 is exemplified below:

Step 1. A small known amount (approximately 6 g) of CLOISITE 25Amasterbatch, to make for a final diluted composition of 1.5%·w/w ofCLOISITE 25A, was taken and its moisture content measured at 160° C. for10 min.

Step 2. Depending upon the moisture content of the CLOISITE 25Amasterbatch, known weight of water was added to hydrate a known weightof the masterbatch to a value of approximately 20%·w.w and soaked in atumbler mixer for 60 min.

Step 3. To the tumbler mixer, known weights of A939 (powder, approximatemoisture: 10.5%), PVOH and stearic acid were added to make a final batchweight of 15 kg and mixed for 30 min.

Step 4. The temperature profile used for processing CLOISITE 25Ananocomposites material used was similar to that for CLOISITE 20A.

Step 5. Sheet materials were produced with a thickness of approximately220-250 μm. These sheets were used to make thermoformed trays(approximately 130° C.).

CONCLUSION

Nanocomposite materials prepared in accordance with the examplesexhibited a high degree of exfoliation of the clay, had improvedmechanical and rheological properties and reduced sensitivity tomoisture. They had improved clarity, remaining transparent for over twomonths.

CLOISITE™ 20A nanocomposites provide better overall properties comparedwith CLOISITE™ Na in terms of transparency, with up to 7% improvement.Mechanical properties in machine and transverse directions have bettertolerance due to better dispersion and exfoliation of the clay, whichindicated better isotropic morphology that will be of benefit inthermoforming processes.

The invention claimed is:
 1. A substantially exfoliated nanocompositematerial including derivatized starch, between 0.1 and 5% by weighthydrophobically modified layered silicate clay, and 5 to 30% by weightwater based on the weight of the nanocomposite material, wherein saidstarch has an amylose content of greater than 50% and is intercalatedbetween clay platelets, and the hydrophobically modified layeredsilicate clay is clay modified by exchange with a surfactant comprisinglong chain alkyl groups wherein no hydroxyl or carboxyl substituents areattached to a long chain alkyl, and wherein said nanocomposite materialhas an optical absorbance coefficient which is at least 25% lower thanthat of said nanocomposite material absent the hydrophobically modifiedlayered silicate clay.
 2. The substantially exfoliated nanocompositematerial of claim 1 wherein the total amount of clay present is between0.1% and 3%·w/w.
 3. The substantially exfoliated nanocomposite materialof claim 1 wherein the total amount of clay present is between 0.5% and2%·w/w.
 4. The substantially exfoliated nanocomposite material of claim1, including more than one hydrophobically modified layered silicateclay.
 5. The substantially exfoliated nanocomposite material of claim 1further including one or more plasticisers.
 6. The substantiallyexfoliated nanocomposite material of claim 1 further including one ormore water-soluble polymers.
 7. The substantially exfoliatednanocomposite material of claim 1 further including one or moreprocessing aids.
 8. The substantially exfoliated nanocomposite materialof claim 1 wherein the hydrophobically modified layered silicate claycomprises a clay modified by exchange with a surfactant comprising amono- or di-C₁₂-C₂₂ alkylammonium ion.
 9. The substantially exfoliatednanocomposite material of claim 8, wherein no polar substituents areattached to an alky chain of the mono- or di-C₁₂-C₂₂ alkylammonium ion.10. The substantially exfoliated nanocomposite material of claim 8,wherein no hydroxyl or carboxyl substituents are attached to an alkychain of the mono- or di-C₁₂-C₂₂ alkylammonium ion.
 11. Thesubstantially exfoliated nanocomposite material of claim 1, wherein thestarch is an acetylated starch, a starch succinate, a carboxymethylatedstarch or a hydroxyalkylated starch.
 12. The substantially exfoliatednanocomposite material of claim 1, wherein the starch is ahydroxypropylated starch.
 13. The substantially exfoliated nanocompositematerial of claim 1, wherein the starch is a hydroxypropylated starchand said surfactant comprises a mono- or di-C₁₂-C₂₂ alkylammonium ion,and wherein no hydroxyl or carboxyl substituents are attached to analkyl chain of the mono- or di-C₁₂-C₂₂ alkylammonium ion.
 14. Thesubstantially exfoliated nanocomposite material of claim 1 wherein saidnanocomposite material has an optical absorbance coefficient betweenabout 260 m⁻¹ and about 308 m⁻¹.
 15. A substantially exfoliatednanocomposite material including derivatized starch, between 0.1 and 5%by weight hydrophobically modified layered silicate clay, and 5 to 30%by weight water based on the weight of the nanocomposite material,wherein said starch has an amylose content of greater than 50% and isintercalated between clay platelets, and the hydrophobically modifiedlayered silicate clay is clay modified by exchange with a surfactantcomprising long chain alkyl groups wherein no hydroxyl or carboxylsubstituents are attached to a long chain alkyl, and wherein saidnanocomposite material has an optical absorbance coefficient betweenabout 260 m⁻¹ and about 308 m⁻¹.
 16. Packaging made from materialincluding the substantially exfoliated nanocomposite material ofclaim
 1. 17. A process for preparing the substantially exfoliatednanocomposite material of claim 1, including a step of mixing the starchhaving an amylose content of greater than 50% with the hydrophobic clayto form a master batch.